The dynamic duo collaborated to harmonize in the Bee Gee-est way on a series of Halloween-themed phrases. (Think corn maze, leaf pile, horn of plenty.)

Barry Gibb and Jimmy Fallon faced off in a battle of fall-themed songs on The Tonight Show on Wednesday night in a bit called "Silhouette Singing."

You have to be pretty confident to go toe-to-toe with the Bee Gees legend in a sing-off, but Fallon, of course, has a bit of history singing in his best Gibb voice from his years hosting "The Barry Gibb Talk Show" on Saturday Night Live.

Gibb came on to promote his first-ever solo album, Here in the Now. In the bit he dressed as 70-year-old Barry, while Fallon went for vintage Gibb in a scene from the singer's fake children's series.

The dynamic duo collaborated to harmonize in the Bee Gee-est way on a series of Halloween-themed phrases. (Think corn maze, leaf pile, horn of plenty.)